\begin{thebibliography}{9}
  \bibitem{stroustrup}
    Bjarne Stroustrup, 
    \textbf{The C$++$ Programming Language}
    
  \bibitem{cppref}
    http://www.cppreference.com, 
    \textbf{Manual de Referencia C $++$}
  
    \bibitem{burden}
    Richard L. Burden / J Douglas Faires, 
    \textbf{An'alisis Num'erico}
    
    \bibitem{Internez}
    Internet
    \textbf{www.wikipedia.org}
    
\end{thebibliography}
